Zilog Z8PE002 Manuel d'utilisateur télécharger pdf (Page 33)

Z8PE002

ZiLOG

Z8Plus OTP Microcontroller

DS008700-Z8X0799 P R E L I M I N A R Y 33

RESET CONDITIONS

After a

RESET

, the timers are disabled. See Table 8 for timer

control, value, and auto-initialization register status after

RESET

I/O PORTS

The

Z8Plus

dedicates 14 lines to input and output. These lines

are grouped into two ports known as Port A and Port B. Port

A is an 8-bit port, bit programmable as either inputs or outputs.

Port B can be programmed to provide either standard in-

put/output, or the following special functions:

output,

comparator input,

SMR

input, and external interrupt inputs.

All pins except

PB5

include push-pull CMOS outputs. In

addition, the outputs of Port A on a bit-wise basis can be

configured for open-drain operation.The ports operate on

a bit-wise basis. As such, the register values for/at a given

bit position only affect the bit in question.

Each port is defined by a set of four control registers (Figure 26).

Directional Control and Special Function

Registers

Each port on the

Z8Plus

features a dedicated directional con-

trol register that determines (on a bit-wise basis) if a given

port bit operates as input or output.

Each port on the Z8Plus features a special function register

(

SFR

) that, in conjunction with the

directional control reg-

ister

, implements (on a bit-by-bit basis) any special func-

tionality that can be defined for each particular port bit.

Input and Output Value Registers

Each port features an Output Value Register and an input

value register. For port bits configured as an input by means

of the

directional control register

, the input value register

Figure 26. Port A Conﬁguration with Open-Drain Capability and Schmitt-Trigger

PA0–PA7

PTAIN Bit n

N = 0...7

PTAOUT Bit n

N = 0...7

PTASFR Bit n

N = 0...7

PTADIR Bit n

N = 0...7

Table 14. I/O Ports Registers

Port B Special Function 0D7H PTBSFR

Port B Directional Control 0D6H PTBDIR

Port B Output Value 0D5H PTBOUT

Port B Input Value 0D4H PTBIN

Port A Special Function 0D3H PTASFR

Port A Directional Control 0D2H PTADIR

Port A Output Value 0D1H PTAOUT

Port A Input Value 0D0H PTAIN

1 2 ... 28 29 30 31 32 33 34 35 36 37 38 ... 47 48

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Zilog Z8PE002 Manuel d'utilisateur Page 33

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